Relative changes in tumor volumes for vehicle, G-CSF, IL-12 pre-only, IL-12 post-only and IL-12 pre-post treatment groups following chemotherapy. Changes in tumor volumes over the course of the experiment are shown for the EL4 lymphoma tumor model (A) and the Lewis Lung cancer tumor model (B). IL-12 treatment significantly reduces tumor growth following cyclophosphamide treatment in late stage tumor models. In the EL4 tumor model, treatment with IL-12 pre-post or IL-12 post-only significantly reduced tumor growth (%T/C < 50%), as compared to both the G-CSF vehicle control groups at the end point of tumor growth assessments. In the Lewis lung cancer model, the IL-12 pre-post and IL-12 pre-only treatment groups yielded a significant reduction in tumor growth (%T/C < 50%), as compared to both the G-CSF and vehicle control groups at the end point of tumor growth assessments. These tumor models represent a late stage cancers, as compared with the models used for the radiation studies because tumors were apparent at the start of the treatments consisting of cyclophosphamide and cytokine therapy. In the case of the lymphoma model, therapy was initiated when the tumors were very large (about 500 mm3).